Preparation of trihydrazine decaborane [(n2h5)2n2h4b10h10]



United States Patent r 3,402,028 PREPARATION OF TRIHYDRAZINE DECABORANE [(N H N H B I-I Daniel Grafstein, Morristown, and Jack Bobinski, Rockaway, N.J., assignors to Thiokol Chemical Corporation, Bristol, Pa., a corporation of Delaware No Drawing. Original application May 7, 1963, Ser. No. 278,785, now Patent No. 3,269,803, dated Aug. 30, 1966. Divided and this application Oct. 4, 1965, Ser. No. 521,467

4 Claims. (Cl. 23-358) This case is a division of Ser. No. 278,785, filed May 7, 1963, now US. Patent No. 3,269,803.

The present invention relates to novel compounds containing boron and to methods for making the same.

In recentyears, there has been considerable interest in boron-containing compounds because the high heat of combustion of these compounds adapts them for use as rocketfuels. Accordingto the present invention, boron compounds have been prepared, which compounds are useful as intermediates in the preparation of boron-containing polymers useful as propellant binders. Moreover, the compounds of the present invention are themselves useful as high-energy fuels and as fuel additives. The solid products of this invention, either per se or after formation into a polymer, can be used as solid propellants for rocket power plants and other jet-propelled devices when mixed with suitable oxidizers such as ammonium, potassium, or sodium perchlorates, ammonium nitrate, etc. Such propellant mixtures are compounds by a number of techniques known to the art. For example, the mixtures may comprise from 5 to 35 parts by weight of boron-containing materials and from 65 to 95 parts by weight of solid oxidizing agents mixed therewith. In some cases the propellant may also be made by combining the boron compounds and oxidizers with a curable polymer, for example, of the polyethylene, polyurethane, polyester, or polyether types.

' Other products of the invention may be used as additives in high-energy liquid fuels by mixing the products with combustible liquids such as compatible hydrocarbon fuels.'

Furthermore, hydrazine and compounds incorporating the hydrazine radical have also been the subject of intense experimental work because of the low atomic weight of the constituent atoms of hydrazine and the potential energy contained therein, and the consequent desirability of hydrazine and its compounds as rocket-fuel additives which contribute large quantities of energy and gas to the propulsion system. i

It is an object of this invention to provide energetic compounds comprising both borane and hydrazine constituents. It is another object of this invention. to provide energetic fuels and fuel additivesfor reaction motors. It is a further object of this invention to provide processes for producing said energetic compounds. Other objects of this invention are in part obvious and in part pointed out hereinafter.

The products of the present invention are trihydrazine decaborane and dihydrazine decaborane having, respectively, the following formulae:

As written above, these formulae indicate the intramolecular electronic balance. The processes by which the prod nets of the present invention are obtained include methods wherein a decaborane derivative which is more highly substituted with hydrazine than the desired product is destabilized to allow production of the dihydrazine-substituted or trihydrazine-substituted decaborane derivative.

In one embodiment of the present'invention hydrazine is reacted with a class of disubstituted-decaborane derivativeswhich are co-ordination compounds of a Lewis base with decaborane. This reaction takes place in acetonitrile solution and in the presence of water as follows:

N H decaborane co-ordination compound-9 I 2 5 )2( 2 4) 10 1o The substituted decaborane derivativespwhich are use; ful for the embodiment of the invention being discussed, are co-ordination compounds of sulfur with decaborane, B H These co-ordination compounds are formed by. the donation of electrons to the decaborane by the Lewis base. For example, the sulfur atom. in diethyl sulfide, which has the following electronic configuration I is capable of donating electrons to form a covalent bond with a chemical which is electronically disposed to accept such electrons. This type of chemical combination iscalled co-ordinating, and the compounds found thereby are called co-ordination compounds. Decaborane is a suitable co-ordinating compound probably because the tricovalent nature of boron readily allows it to accept electrons available in molecules of diethyl sulfide. These electron-donating compounds are known in the chemical art as Lewis bases.

Compounds useful for the present invention are the dialkyl sulfides, and, preferred among such compounds is diethyl sulfide which forms a co-ordination compound with decaborane by the following reaction:

This reaction is suitably carried out in an inert solvent at room temperature. The alkyl groups in the aforementioned compounds are preferably chosen from among lower alkyls (i.e., 1-4 carbon atoms), but may also be any higher alkyl groups which permit solubility of the co-ordination compound in the solvent chosen as the medium for the reaction.

Bis(diethylsulfide)decaborane, the product of reaction (1) above, is reacted with aqueous hydrazine and in acetonitrile solution. The reaction is as follows:

The product of the reaction is trihydrazine decaborane. The reaction (3) between hydrazine and bis(dialkylsulfide)decaborane proceeds suitably at room temperature (20-30 C.), but is conveniently performed at temperatures below room temperature for ease in controlling reaction rate or maintaining volatile reactants or solvents in the convenient condensed form. J 1

In all cases, the reactants are suitably maintained in contact for a time permitting substantially complete reaction. The reaction time is not critical, and will vary with the reaction temperature, concentration, etc. as is usual in chemical reactions.

In other embodiments of the present invention, decaborane more highly substituted with hydrazine or hydrazinium radicals may be treated to produce lower hydrazine-substituted decaboranes. For example, tetrahydrazine decaborane may be dissolved in a polar liquid such as alcohol or water. Upon recrystallization of the material, trihydrazine decaborane Will appear as the recrystallized solid.

In the recrystallization process, the temperature at which tetrahydrazine decaborane is dissolved and recrystallized is not critical and will vary with the solubility of the material Within a given solvent system at different temperatures. The solvent utilized for this operation will preferably be a polar solvent such as ethyl alcohol, water, etc.

Furthermore, if a mole of tetrahydrazine decaborane is subjected to a vacuum, one mole of hydrazine will be removed and the material will be converted into trihydrazine decaborane. Typically suitable conditions for this process are temperatures in the range of 20 to 75 C. and absolute pressures of from about 1 to Q mm. of Hg.

Another method for converting more highly substituted hydrazine decaboranes to the lower-substituted products is to react the former compounds with a strong acid like trifluoroacetic acid. In this reaction, each molecule of acid will combine with a molecule of hydrazine, which latter is removed from the hydrazine-decaborane compound. Thus, for example, tetrahydrazine decaborane when reacted with two moles of the acid is converted to dihydrazine decaborane, and is converted to trihydrazine decaborane when reacted with one mole of the acid.

The reaction of hydrazine-substituted decaboranes with a strong acid, resulting in the removal of hydrazine therefrom, may be carried out at room temperature, and is a convenient method of preparing the products ofthe present invention. Temperatures above room temperature may be used but care should be taken to avoid an exothermic heating to the decomposition temperature of the reactants. This reaction may proceed between the reactants directly or in solution in an organic solvent. Conventional aliphatic, cycloaliphatic, and aromatic hydrocarbon and oxygenated solvents such as benzene, toluene, ethyl alcohol, hexane, dioxane, and ethers can be employed as will be evident to the organic chemist.

Acids useful in this reaction are strong acids such as trifluoroacetic acid and trichloroacetic acid. Other strong acids may be used effectively when they are chosen in such a way as to avoid side reactions with the solvent medium and the reactants.

In order to point out more fully the nature of the present invention, the following specific examples are given as illustrative embodiments of the present processes and products produced thereby.

Example 1 Three grams of his (diethylsulfide)decaborane were dissolved in 50 ml. of acetonitrile. While this solution was maintained at a temperature below 20 C., 2.7 ml. of aqueous hydrazine, containing 0.8 moles of hydrazine, were slowly added to the solution. As this addition proceeded, a solid formed in the mixture. The mixture was agitated for one hour following the completion of the hydrazine addition; during this period, the quantity of solid precipitate increased. The solid was then recovered by filtration and dried under vacuum. A product yield of 23%, based upon the theoretically possible yield, was realized. The melting point of the trihydrazine decaborane product was 118-120 C.

Example'Z' One-half gram of tetrahydrazine decaborane was dissolved in 260 ml. of boiling ethyl alcohol. After cooling, the recrystallized material was recovered and identified as trihydrazine decaborane by infrared analysis.

49.97%. Experimental: N, 39.04%; H; 10.98%; B, 49.97%.

, The melting point of this material was 119:'l20 C. Product yield was 92% of that yield theoretically possible. I 1

Example 3 A suspension of 2.49 grams of tetrahydrazine decaborane was prepared in 80 ml. of methyl alcohol. To this suspension 15 m1. of trifluoroacetic acid, dissolved in ml. of ethyl alcohol, were added. This additionwas carried out with care taken to maintainthe temperature of the mixture below 20 C. A clear solution resulted. The solution was concentrated by evaporating oif a'large part of the alcohol. On cooling, a quantity of solid precipitated. This material was recovered by filtration and redissolved in a mixture of ethyl and methyl alcohols containing a small amount of trifluoroacetic acid. On recrystallization, a solid product was obtained which melted at 244250 C. The product was dihydrazinium decaborane as indicated by infrared analysis.

Calculated: N-N, 30.39; B, 58.68. Found: N-N, 30.33; B, 58.21.

Example '4 To a suspension of 0.84 gram of trihydrazine deca borane in ml. of methyl alcohol was added 0.38 gram of trifluoroacetic acid. Care was taken to keep the mixture at room temperature during the addition of the acid. The solid product, dihydrazinium decaborane, was isolated by fractional crystallization, and identified by infrared analysis.

We claim:

1. A process for the production of trihydrazine deca borane comprising dissolving tetrahydrazine decaborane in a solvent, causing the dissolved material to recrystallize, and recovering the recrystallized material.

2. A process for the production of trihydrazine decaborane comprising subjecting tetrahydrazine to a vacuum and removing therefrom a molecule of hydrazine to form trihydrazine decaborane.

3. A process for the production of trihydrazine'decaborane comprising stoichiometrically reacting a bis(dialkylsulfide)decaborane with hydrazine, and recovering the trihydrazine decaborane product. i

4. A process as in claim 3 wherein said bis(dialkylsulfide)decab'orane is bis(diethylsulfide)decaborane. I

No referencescited. 

1. A PROCESS FOR THE PRODUCTION OF TRIHYDRZING DECABORANE COMPRISING DISSOLVING TETRAHYDRAZINE DEBARNE IN A SOLVENT, CAUSING THE DISSOLVED MATERIAL TO RECRYSTALLIZE, AND RECOVERING THE RECRYSTALIZED MATERIAL.
 2. A PROCESS FOR THE PRODUCTION OF TRIHYDRAZINE DECABORANE COMPRISING SUBJECTING TETRAHYDRAZINE TO A VACUUM AND REMOVING THEREFROM A MOLECULE OF HYDRAZINE TO FORM TRIHYDRAZINE DECABORANE.
 3. A PROCESS FOR THE PRODUCTION OF TIHYDRAZINE DECABORANE COMPRISING STOICHIOMETRICALLY REACTING A BIS(DIALKYLSULFIDE)DECABORANE WITH HYDRAZINE, AND RECOVERING THE TRIHYDRAZINE DECABORANE PRODUCT. 